1. Field of the Invention
The present invention relates to a mixed reality presentation system and a brightness adjustment method of a virtual light source.
2. Description of the Related Art
Recently, systems applying a technique of mixed reality (MR), which naturally combines the real world with a virtual world without giving a sense of oddness, have increasingly been proposed. These MR systems synthesize object images of the real world which are photographed by an image sensing apparatus, for example, a camera, with images of a virtual world which are drawn by computer graphics (CG). By displaying the synthesized image on a display device such as a head-mounted display (hereinafter referred to as a HMD), the MR systems present mixed reality to MR system users.
These mixed reality presentation systems need to generate a virtual world image while tracking changes in the real world image so as to enhance the sense of mixed reality. For this, the mixed reality presentation systems must acquire in real time the system user's view point and attitude, and display in real time images on a display unit, for example, a HMD, for the user.
Note that the mixed reality presentation systems set the user's view point and attitude, which are measured by a sensor unit, as the virtual view point and attitude in the virtual world. Based on the setting, the mixed reality presentation systems draw a virtual world image using CG, and synthesize the virtual world image with the real world image.
Meanwhile, the HMD presents a sense of mixed reality. For this, the MR system performs image displaying within the user's field of vision using the display unit of the HMD, and the display unit of the HMD includes a CG drawing region. By virtue of this configuration, the MR system user can observe, through the display unit of the HMD, an image which looks as if a virtual object existed in the real world. Moreover, in the world of mixed reality, the MR systems can superimpose virtual CG on a real object. The superimposition enables a user to feel a real object which has an appearance of virtual CG.
In the world of mixed reality so far, objects of the real world have not given any influences on the illumination set in the virtual world. In the real world, if a real object blocks actual illumination, the real object creates a shadow. However, the shadow of the real object is not displayed in virtual CG unless particular processing is performed on the illumination of the virtual world. If the shadow is to be displayed, the processing becomes extremely complicated.
The present invention provide simple and high-speed processing of illumination in a virtual world so as to reflect influences of real objects, for example, shadows, in the virtual world.